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volatilization of fluxes - was: wood ash composition

updated thu 9 aug 01


Ian Currie on wed 8 aug 01

Hi again Craig

>As one moves away from the "c" corner to areas of the grid that
>contain less flux and more alumina and silica it may be just the lower
>proportion of flux to the other components that lessens or eliminates the
>flashing from volatiles and not the fact that the fluxes are chemically
>"bound" by the alumina and silica.

Good question, but I don't think this is happening. It should be possible
to test.

>Some of the potash and soda is still
>becoming volatile but it may not be enough to leave a footprint. The
>reason that I'm thinking about this is that even though there is more Al2O3
>and SiO2 in areas away from the "c" corner, all of this dissociates under
>heat and the fluxes are not bound by the other stuff at high temperatures,
>or are they?

As far as I know, the combination of soda with alumina and silica in a salt
firing happens at high temperatures, and it is this sort of reaction I
assume is happening. What state it is in at high temperature (e.g. Cone 10)
I do not know, but I assume that if alumina and silica are low (e.g.
C-corner glaze) it vaporizes and moves on until it bumps into some alumina
and silica elsewhere (e.g. the clay body nearby). However I am not the
expert here!!

Good luck with your new tests.

>Anyway, those are some of the things playing pinball with my brain in
>regard to this stuff. Perhaps we should discuss this over a pint of Tree
>Frog Ale while gazing across the valley at Mt. Hood?

A Pint?? This may be a 6-Pack problem, Craig!! or even a Slab. (Four
6-Packs = 1 Slab)....
...says he who rarely drinks except when visiting Oregon potters... :)
Wish I was there already!!!!

Talking of Oregon potters.... Hank, I am going to have to put you on a
commission! Thanks! And see you soon.